Routers and Routing Basics CCNA 2

1
Routers and Routing Basics CCNA 2
Chapter 5
2
Introduction

• The first half of this chapter reviews the boot
  process
• The second half examines several topics relating
  to how to copy files to and from the router

3
Managing Cisco IOS Software

• Router Boot Sequence and Loading Cisco IOS Images
• Choosing the Cisco IOS Image During the Router
  Boot Sequence
• Troubleshooting and Verifying the Choice of
  Cisco IOS
• Managing Cisco Router IOS and Configuration Files
• Cisco IOS File System
• Cisco IOS Filenames
• Copying and Managing Cisco IOS Images
• Copying and Managing Cisco IOS Configuration
  Files
• Recovering from Lost Passwords
• Summary

4
Introduction

• Routers perform several functions at
  initialization, including picking which Cisco IOS
  image to load into RAM and use.
• The final initialization step relates to how the
  router finds and picks a configuration file to
  use, typically the startup-configuration is file
  stored in NVRAM.
• To do both steps, the router must find, copy,
  move, and manipulate files that hold IOS images
  and files that contain configuration
• commands.
• This chapter closely examines the options and
  processes that routers use to manage these types
  of files.

5
Router Boot Sequence and Loading Cisco IOS Images

• When an engineer first powers on or reboots a
  router, the router goes through
• a four-step process
• 1. Perform a power-on self test (POST).
• - The POST process happens automatically,
  performing basic hardware tests.
• 2. Load a bootstrap program.
• - The bootstrap program completes the hardware
  testing and initializes software in the router.
• 3. Load an IOS.
• - The router loads an IOS image, enabling the
  router to route IP packets.
• 4. Load a startup configuration file.
• - The router loads an initial configuration
  file, which tells IOS the parameters it needs to
  know things like IP addresses and routing
  protocols to use so that the router can
  successfully route packets.
• - The last three steps require the router to
  copy the files into RAM,

6
Moving the Bootstrap, IOS, and Configuration
Files into RAM

• In most networks
• all the routers simply load the startup-config
  file in NVRAM into RAM as the Running-config file
  during the initialization process.
• in other networks, each router may have
  different settings that affect how each router
  picks which IOS file to load.

7
Configuration Register

• The configuration register is a 16-bit register
  that Cisco
• routers store in a hidden area of NVRAM that is
  not part of the startup-config file.
• The configuration registers value tells the
  router facts about several operating parameters
  including
• Which IOS to load the full image, ROMMON or
  RXBoot.
• The speed of the router console port.
• Whether or not to use the configuration file

8
Changing and Viewing the Configuration Registers
Value

• The configuration register can be viewed using
  the show version command.
• The configuration register can be set in two of
  ways,
• The most commonly used way to set its value is to
  use the config-register global configuration
  command.
• It can also be set from Rommon Mode
• When you set the configuration registers value,
  the value is used only after the router is
  reloaded.

9
Changing and Viewing the Configuration Registers
Value (Continued)

• Example shows the (default) value of the
  configuration register, the user changing the
  value, and the show
• version command stating that the new value will
  not be
• used until the next reload.

10
Changing and Viewing the Configuration Registers
Value (Continued)

• The current value at the end of the example shows
  the
• Current setting (hex 2102) and the setting that
  will be used
• at the next reload of the router (hex 2101).

11
How Routers Use the Boot Field to Choose an IOS
(Continued)
12
Choosing the Cisco IOS Image During the Router
Boot Sequence

• Routers use the following logic to attempt to
  load an IOS
• 1. Load a limited-function IOS based on whether
  the configuration registers last hex digit is
  set to 0 or 1.
• - Engineers can use Step 1 when performing
  certain maintenance the OSs loaded at this step
  cannot route packets, but they can be used for
  some useful functions, such as password recovery.
• 2. Load an IOS based on the configuration of boot
  system commands in the startup-config file.

13
Choosing the Cisco IOS Image During the Router
Boot Sequence (Continued)

• 3. Load the first file in flash memory as the
  IOS.
• - Routers almost always pick their IOS based on
  either Step 2 or Step 3.
• Step 2 and 3 give engineers plenty of choices of
  how they can make the router load the correct IOS
  for normal operation of the router
• 4. Use TFTP broadcasts to find a TFTP server, and
  download an IOS from that server.
• 5. Load a limited-function IOS from ROM.
• - Steps 4 and 5 exist mainly as fail-safe
  mechanisms when the first three steps do not work.

14
The Boot Field

• Routers use the 4 low-order bits of the
  configuration register as the boot field.
• The boot field tells the router what to do in its
  first of the five decision steps (Slides 11, 12).
• Depending on the value of the boot field and the
  model of the router, a router can choose to load
  ROMMON, load RXBoot, or move on to a later step
  in the five-step list for choosing an IOS to load.

15
Comparing ROMMON and RXBoot OSs

• Only older routers, such as the Cisco 1600 and
  2500 series routers, have an RXBoot IOS in ROM.
  Later, Cisco added all the features of the RXBoot
  IOS to ROMMON, so newer routers do not need (and
  do not have) an RXBoot IOS.

16
How Routers Use the Boot Field to Choose an IOS

• If the router loads either ROMMON or RXBoot
  software, the process is complete, waiting for
  the network engineer to do whatever low-level
  maintenance function needs to be done.
• However, depending on the configuration register
  settings, the router may simply move on to Step 2
  or even Step 3 of the process of finding an IOS
  to load.
• The most production routers default to use a boot
  field of 2, because the configuration register
  defaults to 0x2102, which tells the router to
  load the IOS

17
How Routers Use the Boot Field to Choose an IOS
(Continued)

• Software Configuration Bit Meanings
• Bit No. Hex Meaning
• 00-03 0x0000-0x000F Boot Field (see Table B-2)
  
• 06 0x0040 Ignore NVM contents
• 07 0x0080 OEM bit enabled
• 08 0x0100 Break disabled
• 10 0x0400 IP broadcast with all zeros
• 11-12 0x0800-0x1000 Console line speed
• 13 0x2000 Boot default ROM software if
  network boot fails
• 0x4000 IP broadcasts do not have net
  numbers
• 0x8000 Enable diagnostic messages and
  ignore NVRAM
• contents

18
How Routers Use the Boot Field to Choose an IOS
(Continued)

• Explanation of Boot Field (Configuration Register
  Bits 00-03)
• Boot Field Meaning
• 00 Stays at the system bootstrap prompt
• 01 Boots system image on EPROM
• 02-F Specifies a default netboot filename
• Enables boot system commands that override
  default
• netboot filename1

19
Choosing the Cisco IOS Based on boot system
Commands

• The router looks in the startup-config file for
  any boot system commands and loads the IOS file
  listed in the commands.
• The boot system command may fail for one of
  several reasons
• - mistype of a long filename
• - IOS file erased from flash memory by mistake
• - the file may be corrupted
• - hardware error trying to access flash memory.

20
Choosing the Cisco IOS Based on boot system
Commands (Continued)

• Cisco routers provide a couple of ways to prepare
  for cases
• in which the router fails when trying to load the
  IOS listed in
• a boot system command
• 1. Configure multiple boot system commands, and
  the router will try each of them sequentially
  until one of them
• works.
• 2. After the router has tried all the boot system
  commands, it moves on to Step 3, in which the
  router attempts to load the first file it finds
  in flash memory, no matter what its name is.

21
Configuring Multiple boot system Commands
Example 5-2 shows a typical case of how to use
multiple boot system commands in a single
configuration.

• The configuration shows the following four boot
  system commands, with the three extra commands
  giving the engineer extra protection against
  potential problems.

22
Configuring Multiple boot system Commands
(Continued)

• 1. The first boot system command simply
  references the specific IOS image in flash
  memory.
• 2. To be ready for the possibility that the file
  may be accidentally erased, the boot system tftp
  command points to a TFTP server at IP address
  10.1.1.1, but with the same filename. In that
  case, the router attempts to contact the listed
  TFTP server, transfer a copy of the same IOS
  file, and load that into RAM.
• 3. The boot system flash command next tells the
  router to look in flash memory, find the first
  file in flash (more on what first file means in
  the next section), and load that file as the IOS.
• 4. If all these commands fail, the router
  attempts to use the last boot system command,
  boot system rom, which tells the router to load
  ROMMON. This last step would then allow to begin
  the process of recovering and copying the erased
  IOS file back into flash.

23
Configuring Multiple boot system Commands
(Continued)

• If you add or change boot system commands the
  copy running-config startup-config command in the
  example is needed so that the boot system
  commands will not be lost when the router is
  rebooted.
• If the router loads the IOS from the TFTP server
  based on the second boot system tftp command, the
  IOS is copied from the server, into RAM, and
  used the file is not stored in flash.
• If you later add another boot system command, it
  is added to the end of the list of boot system
  commands. If you want to add a new command to the
  middle of the list instead of the end of the
  list, you must delete some of the commands by
  using the no boot system
• command, add the new boot system command, and
  then add the previously deleted commands back
  into the configuration.

24
Loading the First File in Flash Memory

• When a router fails to find and successfully load
  an IOS at Step 1 or 2,
• it then tries one last time to find an IOS in
  flash memory.
• The router looks in flash, finds the first file
  in flash, and attempts to use that file as the
  IOS.
• Example shows the output of a show flash command
  on router R1 with the first file in flash (number
  1 on the left).

25
Broadcasting to Find a Cisco IOS on a TFTP Server

• Most routers have been configured so that they
  choose their IOS images at Step 2 or Step 3.
• Step 4 provides the router with one final effort
  to find and load an IOS.
• At this step, the router broadcasts on all
  interfaces to which a cable has been attached,
  looking for a TFTP server.
• If found, the router asks the TFTP server to send
  the router a specific
• file, with the file using a standard name based
  in part on the routers
• hostname, and in part on the configuration
  register value.

26
Broadcasting to Find a Cisco IOS on a TFTP Server

• Step 4 (TFTP) provides the router with one final
  effort to find and load an IOS.
• At this step, the router broadcasts on all
  interfaces to which a cable has been attached,
  looking for a TFTP server.
• If found, the router asks the TFTP server to send
  the router a specific
• file, with the file using a standard name based
  in part on the routers
• hostname, and in part on the configuration
  register value.

27
Loading a Limited-Function OS from ROM

• If the router has given up trying to load a fully
  functional
• IOS, it goes ahead and loads one of the
  limited-function
• OSs, as follows
• If the router has an RXBoot OS (only on older
  routers), the router loads the RXBoot image.
• If the router does not have an RXBoot OS, the
  router loads ROMMON.
• In both cases, the OS loaded by the router can
  copy an IOS from a
• TFTP server or copy an IOS image from a PC
  attached to the console.

28
Troubleshooting and Verifying the Choice of
Cisco IOS

• Routers fail to load an IOS, or load the wrong
  IOS, for a variety of reasons
• - the configregister and boot system commands
  may have been configured to incorrect values
• - if the boot system commands are configured
  correctly, the files may simply be missing from
  flash memory, or the file may not be on the TFTP
  server.
• When referencing a TFTP server, other problems
  could occur
• - the router may not have a working IP route to
  reach the TFTP server
• - the TFTP server software may not be running at
  the time
• - the router has hardware problems that prevent
  flash memory from
• working.

29
Determining Wrong IOS

• When the router has a possibly wrong IOS loaded,
  first look at the two
• configurable items that impact the five-step IOS
  decision process the
• configuration register and the boot system
  commands.
• See the configuration register only by looking at
  the output of the show
• version command the show running-config and show
  startup-config
• commands do not list the value of the
  configuration register.
• After examining the configuration register,
  examine the boot system
• commands in the startup-config file by using the
  show startup-config
• command.
• It is important to look at the startup-config
  file, because the boot system
• commands will not be used until the router
  reboots, and the running-config
• file will be lost when the router reboots.

30
Determining Which Steps Failed

• After you determine which specific IOS images the
  router
• will attempt to load, verify that the files are
  there and
• accessible.
• Consider the following examples
• For any boot system flashfilename commands, you
  should verify that the file with that name is in
  flash, with the same spelling and capitalization.
  The names are case-sensitive.
• For boot system tftp filename ip-address
  commands, you should verify that the correctly
  spelled filename is on the TFTP server, that TFTP
  server software is installed and running on that
  computer, and that the router can ping the
  servers IP address.

31
Determining Which Steps Failed(Continued)

• For a boot system flash command, with no filename
  listed, make sure the lowest numbered file in
  flash is the IOS file that you want to load.
• In some rare cases, the router hardware may have
  a problem and be
• unable to read the contents of flash memory. In
  these cases, it may be
• best to simply call the Cisco Technical
  Assistance Center (TAC) and
• get advice on how to attack the problem.

32
Cisco IOS File System

• IOS has a file system, named the Cisco IOS File
  System (IFS).
• Three general types of files defined and stored
  by IOS using the IFS

33
Variations of Configuration Commands Styles

• The file system created by Cisco IOS has gone
  through three major
• design steps over the years.
• As a result, todays most current IOS releases
  support three variations
• of commands that reference the configuration
  files
• The pre-Version-10.3 style
• The new style as of Version 10.3 (which is the
  most commonly used style)
• The style of commands that use the full IFS names
  for the
• configuration files.

34
Recently Added Stylesof Configuration File
Commands

• The last column of Table lists prefixes added to
  IOS as part of the IFS.
• These prefixes have
• the same sort of meaning as a drive letter with a
  PCs OS. For example, a PCs hard disk drive may
  be drive letter C.
• With IFS, nvram of course refers to NVRAM, and
  system refers to system files held in RAM,
  including the running-config file.

35
Cisco IFS File System Prefixes

• Table lists the prefixes defined by IFS, along
  with
• a brief description.

36
Cisco IOS Filenames

• Cisco supports a very large set of customer
  requirements. As a result,
• Cisco offers a large number of different IOS
  files to its customers.
• IOS files differs from each other with the four
  main points
• 1. The differences in Cisco IOS versions and
  releases.
• To support the various versions and releases,
  Cisco must create different files for each IOS
  version number and, inside that version, for each
  maintenance release.
• 2. The differences between router model
  series/Cisco IOS platforms.
• 3. The differences in Cisco IOS feature sets.
• 4. Other minor differences, including whether the
  IOS is compressed or relocatable.

37
Common IOS Feature Sets

• IP BaseProvides basic IP routing functions,
  including all the features covered in this book.
• IP VoiceSupports the same features as IP Base,
  plus support for voice sent inside IP packets
  (voice over IP, or VoIP).
• IP/FW 3DESIncludes the features of IP Base, plus
  a firewall feature and Triple Digital Encryption
  Standard (3DES) encryption. This feature set
  provides many security features.
• IP/ADSL/IPX/AT/IBM PlusIncludes IP, IPX, and
  AppleTalk (AT) routing, support for many
  proprietary protocols from IBM, and support for
  asymmetric DSL (ADSL), which is the type of DSL
  most typically found installed in the United
  States today.
• Enterprise ServicesIncludes most every feature
  used in the largest enterprises.

38
Multiple File Formats of IOS Files

• The file format differs mainly on two features
• - Whether the file is compressed
• Compressed IOS files require less space in
  flash memory, but they require more time when
  the router reboots, because the router has to
  uncompress the file before loading it.
• - Whether the file is relocatable
• With a relocatable IOS file, the router does
  not have to copy the whole IOS into RAM, instead
  leaving most of it in flash memory, which saves
  some space in RAM. IOS files that cannot be
  relocated must be fully copied into RAM when the
  IOS is loaded.

39
Cisco IOS Filenames(Continued)

• Cisco names the IOS files so that all four
  different items
• are implied by the name.

40
Copying IOS Files Using copy Command

• The IOS copy command provides a way to copy files
  to
• and from flash memory in the router and a server
  in the
• network. It supports three main protocols
• 1. Trivial File Transfer Protocol (TFTP)
• 2. Remote Copy (RCP)
• 3. File Transfer Protocol (FTP)
• TFTP tends to be the most commonly used option,
  and it
• has been supported in IOS longer than RCP and FTP.

41
Copying from TFTP Server into Flash Memory

• 1. The user enters the copy tftp flash command.
• 2. The router asks for the hostname or IP address
  of the TFTP server and waits for a response.
• 3. The user enters 192.168.119.20 and presses
  Enter.
• 4. The router asks for the name of the source
  file to be taken from the TFTP server and waits
  for a response.
• 5. The user enters C2600-js-l_121-3.bin, presses
  Enter.
• 6. The router asks for the name it should use
  when storing the file in flash memory, which
  defaults to the same name as the source file, as
  shown in brackets. The router then waits for a
  response.

42
Copying from TFTP Server into Flash Memory
(Continued)

• 9. The user presses Enter, taking the default
  action of erasing all the flash files.
• 10. The router asks if the user is sure about
  erasing flash memory, again asking the user to
  confirm.
• 11. The user presses Enter, taking the default
  action of erasing flash memory.
• 12. The router erases flash memory and then
  copies the file. Progress on the erasure of flash
  memory is shown by the routers displaying
  another e every few seconds, and progress on the
  copy is shown by displaying another ! every few
  seconds.

7. The user presses Enter to accept the default
of using the same filename. 8. The router
displays several lines and then asks if the user
wants to erase flash memory before copying the
file. The router then waits for a response.
43
Copying Using the ROMMON tftpdnld Command

• The ROMMON tftpdnld command can work only if the
  following conditions are met
• The IP network is working well enough that the
  broken router can send IP packets to and from a
  TFTP server.
• The TFTP server has the appropriate IOS file
  available for download.

44
Copying Using the ROMMON tftpdnld Command
(Example)
(continued)
45
Environment Variables Needed for the tftpdnld
Command
46
Copying Using ROMMON and Xmodem

• The Xmodem protocol defines a method to transfer
  files over an asynchronous serial line.
• Xmodem was first created to support transferring
  files over dialed links that used modems.
• Because the word transfer was frequently
  abbreviated as xfer, Xmodem seemed like a good
  short name for a protocol for transferring files
  using modems and dialed serial links.

47
Copying Using ROMMON and Xmodem (Continued)

• To transfer an IOS file into a router using the
  Xmodem
• protocol, you need three basic components
• 1. A router running ROMMON software so that the
  ROMMON xmodem command can be used.
• 2. A PC with the IOS file and a terminal emulator
  that supports Xmodemfor example, HyperTerminal.
• 3. A connection between a PC and the router that
  connects to the routers console or the aux ports.

48
Copying Using ROMMON and Xmodem (Continued)

• Using Xmodem to copy a new IOS into a routers
  flash memory should be your last resort when
  trying to get an IOS to load into a Cisco router.
• The first option is to use the IOS copy command
  to copy the correct IOS into flash, assuming you
  can get some copy of IOS up and working.
• If the router cannot load an IOS directly, using
  ROMMON and the tftpdnld command is the next best
  option, but this option requires a working IP
  network and working TFTP server.
• The Xmodem option works when no IOS will load in
  the router and when there is no IP connectivity
  between the router and a TFTP server.

49
Components Required for Xmodem Transfer over the
Console

• Transferring an IOS using Xmodem, with the
  default console speed,
• Is a very slow process.
• To speed up the process, you can change the
  speed of the console port up to its maximum speed
  of 115.2 kbps.

50
Setting the Configuration Register from ROMMON

• To change the speed, you must change the value
  of the configuration register to change the
  register from ROMMON, you need to use the ROMMON
  confreg command.
• The confreg command prompts the user with a
  series of questions.
• The answers to the questions tell ROMMON to what
  value the confi-guration register should be
  changed.
• As it turns out, the console speed can be
  changed by changing some of the bits in the
  configuration register.

51
Setting the Configuration Register from ROMMON
(Continued)

• Example above focuses on how to set the console
  bit rate to a different value, but the command
  allows the user to change any
• of the bits in the configuration register.
• Note that the configuration register does not
  immediately change. It
• requires a reset or power off/on to take effect,
  just like when setting the configuration register
  using the IOS config-register command.
• When you do reload the router, the console bit
  rate changes, so the
• Terminal emulator settings also need to be
  changed to match the same speed in this case,
  115.2 kbps.

52
Steps Used by the xmodem Command
A Router Preparing to Receive a File Using
ROMMONs xmodem Command

• Regardless of the console speed, the transfer of
  the IOS file from the PC to the routers flash
  memory requires two basic steps
• Step 1 The engineer issues the ROMMON xmodem
  command to prepare the router to receive the
  file.
• Step 2 The engineer tells the terminal emulator
  to send the file using Xmodem.

53
Starting an Xmodem File Transfer Using a Terminal
Emulator
54
After Transfer is Done

• To get the router working again, you need to
  follow these steps
• Step 1 Use the confreg command to reset the
  configuration
• register to its original setting.
• Step 2 Use the reset command to reload the
  router (or turn it off and then on).
• Step 3 Change back the terminal-emulator
  configuration to
• use a speed of 9600 bps.

55
Verifying Cisco IOS Images

• The two main types of information about IOS
  images
• include the following
• 1. Information about the IOS that the router is
  currently using.
• 2. Information that determines what IOS images
  the router will attempt to load the next time it
  reboots.

56
Important show Commands When Working with IOS
Files
57
Key Items in the Output of the show version
Command

• The show version command lists most of the
  information relevant to examining IOS files.

58
Copying and Managing Cisco IOS Configuration
Files

• IOS includes two main configuration files
• 1. startup-configStored in NVRAM and holds the
  configuration that will be used the next time
  the router reloaded.
• 2. running-configSits in RAM and holds the
  configuration commands currently being used in
  the router.
• Copying the configuration to a computer allows
  the engineer to keep backup copies of the
  configuration.
• Copying the configuration into the running-config
  file may give the engineer a more convenient
  method for typing and adding configuration
  commands to routers.

59
Copying Configuration Files Using the IOS copy
Command

• The process of copying configuration files
  between a router
• and a TFTP server requires that you use
• - the copy tftp running-config command to the
  file from the server into the running-config file
• - the copy running-config tftp command to the
  file from the routers running-config file to the
  TFTP server.

60
Copying Configuration Files Using the IOS copy
Command (Continued)
Copying to and from a TFTP Server

• Step 1 Enter either the copy tftp running-config
  or copy running-config tftp command, and press
  Enter.
• Step 2 Respond to the prompt with the IP address
  or hostname of the TFTP server, and press Enter.
• Step 3 Respond to the next prompt with the
  filename to be used on the
• TFTP server, and press Enter.
• Step 4 Respond to the third prompt by simply
  pressing Enter to confirm that you want to
  transfer the file.

61
Copying Configuration Files Using Copy and Paste

• Most Windows-based applications have a
  copy-and-paste feature that makes it easy to
  duplicate text between applications. Because
• configuration files are all text-based, they can
  be copied and pasted as well.
• There are two variations on how to use the
  copy-and-paste feature of a PC to copy
  configuration commands to and from the
  running-config file in a router
• - use a text-editor window and a
  terminal-emulator window, copying the text
  between the two
• - use some text-capture and text-sending
  features typically included in most terminal
  emulators.

62
Copy and Paste Between the Emulator and a Text
Editor

• Every PC OS supports a variety of applications
  called text editors. All of these applications
  allow the user to enter text into the editor,
  change the text, and save the file as text file.
• For example, Notepad on Microsoft OSs is
  relatively simple, while Microsoft Word is quite
  sophisticated.
• For the purpose of copying the configuration to
  and from a router, a simple text editor such as
  Notepad will work just fine.

63
Entering Commands into a Text Editor and Copying
the Command Text

• Use Notepad (or any other editor) to enter
  configuration commands
• select and copy the text. After that the PC is
  ready to paste the text into another window.
• The picture shows a window from a PC, with the
  Notepad editor.
• The user has entered four configuration commands,
  selected the text, and is ready to select the
  Copy
• function on the Edit menu.

64
Pasting Text into a Terminal-Emulator Window

• When the PC has a copy of the text that was shown
  in the text-editor screen, the user can paste the
  text into another window.
• To add the configuration commands
• to a routers configuration
• - log in to the router using a terminal emulator,
  from that same PC, and get into configuration
  mode.
• - in configuration mode use the Paste feature of
  the OS, which sends the text to the chosen
  windowin this case, the terminal emulator.
• Pasting the text into the window works just like
  someone typing the exact same text into the
  window.

65
Using copy-and-paste

• When configuring the same commands on many
  routers, you can enter the commands into an
  editor on the PC and then copy and paste the
  commands into several routers configurations,
• saving time and effort.
• You can also copy from the terminal-emulator
  window and paste the text into the text editor to
  make backup copies of the configuration.
• While performing labs during the class, you can
  easily copy and paste from the terminal emulator
  into an editor such as Notepad and then save the
  file on your PC for later reference.

66
Using a Terminal Emulators Text Capture Feature

• Most terminal emulators have a feature (that is
  the a variation of the copy-and-paste process) by
  which you can tell the emulator to capture all
  text displayed by the emulator and then put the
  text into a text file.
• Emulators also typically have a feature by which
  you can tell the emulator to take the content of
  a text file and send it into the window as if you
  had entered all the text in the file into that
  window.

67
Using a Terminal Emulators Text Capture Feature
(Continued)

• These two features together allow network
  engineers to use a simple
• three-step process to back up the configurations
  of routers
• Step 1 Use the emulators text-capture feature to
  capture the output of
• a show running-config or show startup-config
  command.
• Step 2 Because the capture process may capture
  extraneous characters or other unneeded text,
  edit the file to prepare it to be used as a
  backup configuration file.
• Step 3 Should the router ever lose its
  configuration, use the emulators
• send text file feature to send the contents of
  the backup configuration file back to the router
  and into configuration mode.

68
Using a Terminal Emulators Text Capture Feature
(Continued)

• For Step 1, you need to use the emulators
  text-capture feature to capture the
• output of a show running-config command.
• The following list describes how to use the
  text-capture feature of
• the HyperTerminal emulator to make a backup copy
  of the running-config file
• Step 1 In the HyperTerminal window, choose
  Transfer gt Capture Text.
• Step 2 Specify the name for the text file to the
  capture configuration.
• Step 3 Click the Start button to start capturing
  text.
• Step 4 Display the configuration to the screen by
  entering show runningconfig.
• Step 5 Press the Spacebar when each --More--
  prompt appears, which
• continues with the configuration until the end is
  reached.
• Step 6 When the complete configuration has been
  displayed, stop the capture
• by choosing Transfer gt Capture Text gt Stop, as
  shown in Figure 5-7.

69
Stopping the HyperTerminal Text-Capture Feature

• If the user has already started the text capture,
  so the menu shows only an option to stop the
  current capture.
• If no text capture were currently in progress,
  the menu would list a Start option instead.

70
Editing File From Notepad

• To edit the file from Notepad, complete the
  following steps
• Step 1 Open the Notepad application. (On
  Microsoft OSs, go to Start gt
• Run, enter notepad, and click OK).
• Step 2 Select File gt Open.
• Step 3 Find the captured file and select it.
• Step 4 Click Open.
• The following types of lines typically need to be
  deleted to be ready to paste the
• configuration back into the router
• show running-config
• Building configuration...
• Current configuration
• - More -
• Any lines that appear after the word End

71
Additional Features

• You can also add comment lines to document the
  configuration. When you are pasted back into the
  router, the router ignores and discards the
  comment lines, but they are useful when reviewing
  the file on your PC.
• To add a comment line, simply add a new line to
  the file, with the first character being an
  exclamation mark (!).
• Additionally, you may also want to add the no
  shutdown command
• under each interface so that when the
  configuration is pasted back into the router, the
  router attempts to bring up each interface.
• Finally, dont forget to save the file. With
  Notepad, choose
• File gt Save.

72
Restoring Backup Configuration

• That last step occurs when you want to add the
  configuration back into
• the router. You can then restore the backup
  configuration from a
• HyperTerminal session by using the text-transfer
  feature
• Step 1 Log in to the router using HyperTerminal.
• Step 2 Go into router global configuration mode.
• Step 3 From the HyperTerminal window, choose
• Transfer gt Send Text File.
• Step 4 Select the name of the file for the saved
  backup configuration.

73
Restoring Backup Configuration(Continued)

• Step 5 The lines of the file are entered into the
  router as if they are being typed. Look for any
  errors.
• Step 6 After the configuration is entered, press
  Ctrl-Z to exit global
• configuration mode.
• Step 7 Restore the startup configuration with
• copy running-config startup-config.

74
Recovering from Lost Passwords

• If you forget the console, telnet, and enable
  passwords on a router,
• you need to find a way to get back into the
  router and reset or recover the passwords.
• The password recovery process requires reboot the
  router and tell it to ignore the configuration in
  NVRAM. If the router manages to boot without
  using the configuration in NVRAM, the router will
  not have any passwords configured it will have
  nothing configured.
• From that point, the engineer can log in from the
  console and get into enable mode, and the router
  will not request a password.
• Then the engineer can reconfigure new passwords
  or display any unencrypted passwords using the
  show startup-config command.

75
Password Recovery Process

• The overall password recovery process runs like
  this
• Step 1 Connect to the console of the router.
• Step 2 Reload the router (or turn it off and back
  on).
• Step 3 Press the Break key on the keyboard in the
  first 30 seconds of the reload.
• Step 4 When the router responds by entering
  ROMMON mode, change the configuration register
  (with the confreg ROMMON command) to tell the
  router to ignore the startup-config file.
  (Typically, that means setting the configuration
  registers third octet to 4for example, 0x2142.)

76
Password Recovery Process(Continued)

• Step 5 Reload the router (typically using the
  reset ROMMON command).
• Step 6 When the router has completed booting, log
  in to the router from
• the console, and enter enable mode.
• Step 7 Use the copy startup-config running-config
  command to load the configuration into the
  router.
• Step 8 Enter configuration mode, and reconfigure
  new passwords.
• This list does not include every detail, but it
  does give the overall flow of the process used on
  most every model of Cisco router.
• Go to Cisco.com and use the search tool to search
  for password
• for detailed password recovery procedures.

77
Summary

• A Cisco router chooses the location from which it
  should load a
• stored copy of an IOS image based on several
  rules
• - first, router attempt to load an IOS from
  flash memory
• - if that fails, the router attempts to load an
  IOS from a TFTP server
• - and if that fails, the router may have to load
  a limited-function OS
• such as ROMMON or RXBoot.
• You can control this process by changing the boot
  field of the configuration register (the last 4
  bits, or last hex digit) using the
  config-register command, and by configuring boot
  system commands.

78
Summary (Continued)

• Under normal conditions, a router first looks for
  boot system commands in the startup-config file
• - if multiple boot system commands exist, the
  router attempts each command, in order, until it
  manages to successfully load an IOS
• - if all the boot system commands fail, the
  router then attempts to load the first file found
  in flash memory.
• To troubleshoot the boot process, look at the
  boot system commands in the startup-config file
  by using the show startup-config command.
• Additionally, look at the configuration
  registers value as listed at the end of the show
  version command output.
• Note that the configuration register value
  changes only when the router is reloaded.

79
Summary (Continued)

• Cisco creates the filenames of IOS files with
  four parts
• 1. The hardware platform
• 2. A code that represents the feature set
• 3. A code that represents the file format
• 4. The version and release number
• Cisco routers use two internal configuration
  files the startup-config file and the
  running-config file. The startup-config file is
  stored in NVRAM and is copied into RAM to be used
  as the running-config file when the router is
  reloaded.
• While configuring a router, periodically save
  the running-config file using the copy
  running-config startup-config command, so the
  files end up being identical.

80
Summary (Continued)

• It is useful and important to keep a backup copy
  of the configuration files on an external device.
  The copy running-config tftp command can be used
  to copy the configuration to an external
• TFTP server.
• Use a text editors simple copy-and-paste
  mechanisms when logged in to a router to copy the
  output of a show running-config command into a
  file.
• Most terminal emulators support the ability to
  perform a text-capture function, which causes the
  emulator to copy everything sent to the screen
  into a text file.